Analysis of Taste Quality Differences Between High and Low Grades of Ninghong Tea: From the Perspective of Sensory, Metabolite, and Taste Activity Values

In this study, the taste quality difference between high (Ninghong-Jinhao tea, JH, unfolded fresh leaves) and low (Ninghong-Congou tea, CG, unfurled fresh leaves) grades of Ninghong tea (unique black tea) was analyzed from the perspective of sensory omics, non-targeted metabolomics, and chemical dose. JH was characterized by sweetness and mellowness with umami, while CG was characterized by sweetness and thickness. A total of 94 differential metabolites contribute to the quality difference between two grades. Further quantitative analysis revealed that JH exhibited a high accumulation of amino acids, catechins, and theaflavins, while CG demonstrated a high accumulation of water extract, tea polyphenols, flavonol glycosides, and saccharides. Taste activity values (TAVs) analysis revealed that the key taste components of JH and CG were catechin, epigallocatechin gallate, three theaflavins, caffeine, myrictin-3-O-glucoside, quercetin-3-O-rutinoside, quercetin-3-O-glucoside, quercetin-3-O-galactoside, kaempferol-3-O-rutinoside, kaempferol-3-O-glucoside, and gallic acid. Among the identified compounds, the TAVs of five flavonol glycosides in Ninghong tea were found to be greater than 10 for the first time. This study is helpful to understand the taste quality difference between different grades of Ninghong tea from the molecular sensory level, providing a scientific foundation for quality improvement and targeted regulation.